Whether the animation should additionally be applied to all descendants of the matched elements. This feature should be used with caution as the cost of determining which descendants to animate can be very expensive, and grows linearly with the number of descendants.

A Boolean indicating whether to place the animation in the effects queue. If false, the animation will begin immediately. As of jQuery 1.7, the queue option can also accept a string, in which case the animation is added to the queue represented by that string.

Similar to native CSS transitions, jQuery UI's class animations provide a smooth transition from one state to another while allowing you to keep all the details about which styles to change in CSS and out of your JavaScript. All class animation methods, including .addClass(), support custom durations and easings, as well as provide a callback for when the animation completes.

Not all styles can be animated. For example, there is no way to animate a background image. Any styles that cannot be animated will be changed at the end of the animation.

This plugin extends jQuery's built-in .addClass() method. If jQuery UI is not loaded, calling the .addClass() method may not fail directly, as the method still exists. However, the expected behavior will not occur.